JBRA Assisted Reproduction 2025;29(Suppl.2 SBRA 2025):212
Poster Presentation
29^th Annual Congress of the SBRA. São Paulo/SP - Brazil, 2025
doi: 10.5935/1518-0557.20263871

P-200. Rescue IVM in poor responders: incremental gain of usable and euploid blastocysts – Retrospective Cohort 2021–2025 in a Private Center

Carine Lima¹, Andressa Gonçalves Mendes¹, Amanda Oliveira¹, Marcello Pereira Valle¹

¹ Origen Rio - Rio de Janeiro – RJ - Brasil

Objective: Patients with a low number of retrieved metaphase II (MII) oocytes in IVF cycles often face reduced chances of obtaining viable embryos. In this context, this study aimed to assess the effectiveness of in vitro maturation (IVM) of prophase I (P1) and metaphase I (MI) oocytes, focusing on usable blastocyst rates and comparing outcomes with MII oocytes.
Methods: This retrospective observational study analyzed 37 treatments conducted between 2021 and the first quarter of 2025 at a private assisted reproduction center. Included cases involved patients with mean age of 38±3.7 undergoing rescue IVM of oocytes at the P1 and MI stages. Immature oocytes were cultured overnight in CSCM-NXC or Global Total LP medium, with maturation status assessed at 7 a.m. on Day 1 (D1) of development. MII oocytes retrieved on Day 0 (D0) underwent intracytoplasmic sperm injection (ICSI) 39–40 hours after the trigger. Oocytes that reached MII on D1 were injected immediately after maturation assessment. Evaluated outcomes included fertilization rates, viable blastocyst formation, and euploidy. Statistical significance was tested using Fisher's exact test.
Results: A total of 265 oocytes were analyzed: 129 MII, 47 MI, and 89 P1. Immature oocytes that reached MII stage on D1 were fertilized through ICSI. Fertilization rates were comparable among the groups (MII: 68%; MI: 60%; P1: 63%; p>0.05). For viable blastocyst formation, MII oocytes outperformed P1 (56% vs. 38%; p=0.04), but MII and MI showed similar results (56% vs. 50%; p=0.66). This suggests that MI oocytes matured in vitro may have comparable developmental potential to in vivo matured MII oocytes. Overall, 54% of cases obtained at least one additional viable blastocyst from IVM-matured oocytes. Euploidy rates showed no statistically significant differences, although MI oocytes had a higher tendency toward euploid embryos compared to P1 (54% vs. 19%; p=0.0641). Among patients undergoing genetic testing, 27% obtained at least one additional euploid embryo from IVM-matured oocytes.
Conclusion: Although rescue IVM has been applied in assisted reproduction for over a decade, there is still no standardized, widely accepted protocol—partly due to the limited availability of specialized culture media and materials. Nevertheless, growing evidence suggests that r-IVM can be a promising strategy in specific scenarios, particularly for patients with low ovarian reserve or poor ovarian response to stimulation (Rienzi et al., 2025). In such cases, the technique may increase the chance of obtaining at least one additional viable blastocyst, potentially improving treatment outcomes. Previous studies have shown that rescue IVM could yield, on average, 1.5 extra embryos for transfer in women with low ovarian reserve (Lee et al., 2015), supporting its role in individualized treatment planning. Although preliminary, the findings of the present study are consistent with previously reported trends, supporting the potential benefit of r-IVM of immature oocytes in enhancing viable blastocyst formation. A noteworthy consideration is oocyte cytoplasmic maturation, which concludes hours after the extrusion of the first polar body. This timing may explain why MI oocytes, when matured in vitro, perform similarly to in vivo matured MII oocytes in terms of fertilization, blastocyst development, and euploidy. In 2024, Schoolcraft and Katz-Jaffe reported that IVM-derived oocytes have a higher risk of chromosomal abnormalities. However, pregnancy and implantation outcomes for euploid embryos were comparable between those derived from D0 MII oocytes and those obtained after IVM, reinforcing that rescue IVM could be a viable option to optimize laboratory results in selected cases.